[PATCH] MIPS: Refactor 'clear_page' and 'copy_page' functions.

[PATCH] MIPS: Refactor 'clear_page' and 'copy_page' functions.

[Steven J. Hill]

From: "Steven J. Hill" <sjhill@mips.com>

Remove usage of the '__attribute__((alias("...")))' hack that aliased
to integer arrays containing micro-assembled instructions. This hack
breaks when building a microMIPS kernel. It also makes the code much
easier to understand.

Signed-off-by: Steven J. Hill <sjhill@mips.com>
---
 arch/mips/mm/Makefile     |    4 +--
 arch/mips/mm/page-funcs.S |   49 +++++++++++++++++++++++++++++++++
 arch/mips/mm/page.c       |   67 ++++++++++++---------------------------------
 3 files changed, 69 insertions(+), 51 deletions(-)
 create mode 100644 arch/mips/mm/page-funcs.S

diff --git a/arch/mips/mm/Makefile b/arch/mips/mm/Makefile
index 4aa2028..fd6203f 100644
--- a/arch/mips/mm/Makefile
+++ b/arch/mips/mm/Makefile
@@ -3,8 +3,8 @@
 #
 
 obj-y				+= cache.o dma-default.o extable.o fault.o \
-				   gup.o init.o mmap.o page.o tlbex.o \
-				   tlbex-fault.o uasm.o
+				   gup.o init.o mmap.o page.o page-funcs.o \
+				   tlbex.o tlbex-fault.o uasm.o
 
 obj-$(CONFIG_32BIT)		+= ioremap.o pgtable-32.o
 obj-$(CONFIG_64BIT)		+= pgtable-64.o
diff --git a/arch/mips/mm/page-funcs.S b/arch/mips/mm/page-funcs.S
new file mode 100644
index 0000000..901c2bc
--- /dev/null
+++ b/arch/mips/mm/page-funcs.S
@@ -0,0 +1,49 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Micro-assembler generated clear_page/copy_page functions.
+ *
+ * Copyright (C) 2012  MIPS Technologies, Inc.
+ */
+#include <asm/asm.h>
+#include <asm/regdef.h>
+
+/*
+ * Maximum sizes:
+ *
+ * R4000 128 bytes S-cache:		0x058 bytes
+ * R4600 v1.7:				0x05c bytes
+ * R4600 v2.0:				0x060 bytes
+ * With prefetching, 16 word strides	0x120 bytes
+ */
+EXPORT(__clear_page_start)
+#ifdef CONFIG_SIBYTE_DMA_PAGEOPS
+LEAF(clear_page_cpu)
+#else
+LEAF(clear_page)
+#endif
+1:	j	1b		/* Dummy, will be replaced. */
+	.space 288
+END(clear_page)
+EXPORT(__clear_page_end)
+
+/*
+ * Maximum sizes:
+ *
+ * R4000 128 bytes S-cache:		0x11c bytes
+ * R4600 v1.7:				0x080 bytes
+ * R4600 v2.0:				0x07c bytes
+ * With prefetching, 16 word strides	0x540 bytes
+ */
+EXPORT(__copy_page_start)
+#ifdef CONFIG_SIBYTE_DMA_PAGEOPS
+LEAF(copy_page_cpu)
+#else
+LEAF(copy_page)
+#endif
+1:	j	1b		/* Dummy, will be replaced. */
+	.space 1344
+END(copy_page)
+EXPORT(__copy_page_end)
diff --git a/arch/mips/mm/page.c b/arch/mips/mm/page.c
index cc0b626..98f530e 100644
--- a/arch/mips/mm/page.c
+++ b/arch/mips/mm/page.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2003, 04, 05 Ralf Baechle (ralf@linux-mips.org)
  * Copyright (C) 2007  Maciej W. Rozycki
  * Copyright (C) 2008  Thiemo Seufer
+ * Copyright (C) 2012  MIPS Technologies, Inc.
  */
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -71,45 +72,6 @@ static struct uasm_reloc __cpuinitdata relocs[5];
 #define cpu_is_r4600_v1_x()	((read_c0_prid() & 0xfffffff0) == 0x00002010)
 #define cpu_is_r4600_v2_x()	((read_c0_prid() & 0xfffffff0) == 0x00002020)
 
-/*
- * Maximum sizes:
- *
- * R4000 128 bytes S-cache:		0x058 bytes
- * R4600 v1.7:				0x05c bytes
- * R4600 v2.0:				0x060 bytes
- * With prefetching, 16 word strides	0x120 bytes
- */
-
-static u32 clear_page_array[0x120 / 4];
-
-#ifdef CONFIG_SIBYTE_DMA_PAGEOPS
-void clear_page_cpu(void *page) __attribute__((alias("clear_page_array")));
-#else
-void clear_page(void *page) __attribute__((alias("clear_page_array")));
-#endif
-
-EXPORT_SYMBOL(clear_page);
-
-/*
- * Maximum sizes:
- *
- * R4000 128 bytes S-cache:		0x11c bytes
- * R4600 v1.7:				0x080 bytes
- * R4600 v2.0:				0x07c bytes
- * With prefetching, 16 word strides	0x540 bytes
- */
-static u32 copy_page_array[0x540 / 4];
-
-#ifdef CONFIG_SIBYTE_DMA_PAGEOPS
-void
-copy_page_cpu(void *to, void *from) __attribute__((alias("copy_page_array")));
-#else
-void copy_page(void *to, void *from) __attribute__((alias("copy_page_array")));
-#endif
-
-EXPORT_SYMBOL(copy_page);
-
-
 static int pref_bias_clear_store __cpuinitdata;
 static int pref_bias_copy_load __cpuinitdata;
 static int pref_bias_copy_store __cpuinitdata;
@@ -282,10 +244,15 @@ static inline void __cpuinit build_clear_pref(u32 **buf, int off)
 		}
 }
 
+extern u32 __clear_page_start;
+extern u32 __clear_page_end;
+extern u32 __copy_page_start;
+extern u32 __copy_page_end;
+
 void __cpuinit build_clear_page(void)
 {
 	int off;
-	u32 *buf = (u32 *)&clear_page_array;
+	u32 *buf = &__clear_page_start;
 	struct uasm_label *l = labels;
 	struct uasm_reloc *r = relocs;
 	int i;
@@ -356,17 +323,17 @@ void __cpuinit build_clear_page(void)
 	uasm_i_jr(&buf, RA);
 	uasm_i_nop(&buf);
 
-	BUG_ON(buf > clear_page_array + ARRAY_SIZE(clear_page_array));
+	BUG_ON(buf > &__clear_page_end);
 
 	uasm_resolve_relocs(relocs, labels);
 
 	pr_debug("Synthesized clear page handler (%u instructions).\n",
-		 (u32)(buf - clear_page_array));
+		 (u32)(buf - &__clear_page_start));
 
 	pr_debug("\t.set push\n");
 	pr_debug("\t.set noreorder\n");
-	for (i = 0; i < (buf - clear_page_array); i++)
-		pr_debug("\t.word 0x%08x\n", clear_page_array[i]);
+	for (i = 0; i < (buf - &__clear_page_start); i++)
+		pr_debug("\t.word 0x%08x\n", (&__clear_page_start)[i]);
 	pr_debug("\t.set pop\n");
 }
 
@@ -427,7 +394,7 @@ static inline void build_copy_store_pref(u32 **buf, int off)
 void __cpuinit build_copy_page(void)
 {
 	int off;
-	u32 *buf = (u32 *)&copy_page_array;
+	u32 *buf = &__copy_page_start;
 	struct uasm_label *l = labels;
 	struct uasm_reloc *r = relocs;
 	int i;
@@ -595,21 +562,23 @@ void __cpuinit build_copy_page(void)
 	uasm_i_jr(&buf, RA);
 	uasm_i_nop(&buf);
 
-	BUG_ON(buf > copy_page_array + ARRAY_SIZE(copy_page_array));
+	BUG_ON(buf > &__copy_page_end);
 
 	uasm_resolve_relocs(relocs, labels);
 
 	pr_debug("Synthesized copy page handler (%u instructions).\n",
-		 (u32)(buf - copy_page_array));
+		 (u32)(buf - &__copy_page_start));
 
 	pr_debug("\t.set push\n");
 	pr_debug("\t.set noreorder\n");
-	for (i = 0; i < (buf - copy_page_array); i++)
-		pr_debug("\t.word 0x%08x\n", copy_page_array[i]);
+	for (i = 0; i < (buf - &__copy_page_start); i++)
+		pr_debug("\t.word 0x%08x\n", (&__copy_page_start)[i]);
 	pr_debug("\t.set pop\n");
 }
 
 #ifdef CONFIG_SIBYTE_DMA_PAGEOPS
+extern void clear_page_cpu(void *page);
+extern void copy_page_cpu(void *to, void *from);
 
 /*
  * Pad descriptors to cacheline, since each is exclusively owned by a
-- 
1.7.10

Re: [PATCH] MIPS: Refactor 'clear_page' and 'copy_page' functions.

[David Daney]

On 05/24/2012 01:38 PM, Steven J. Hill wrote:
> From: "Steven J. Hill"<sjhill@mips.com>
>
> Remove usage of the '__attribute__((alias("...")))' hack that aliased
> to integer arrays containing micro-assembled instructions. This hack
> breaks when building a microMIPS kernel. It also makes the code much
> easier to understand.
>
> Signed-off-by: Steven J. Hill<sjhill@mips.com>

Looks good to (and even works for) me:

Acked-by: David Daney <david.daney@cavium.com>

> ---
>   arch/mips/mm/Makefile     |    4 +--
>   arch/mips/mm/page-funcs.S |   49 +++++++++++++++++++++++++++++++++
>   arch/mips/mm/page.c       |   67 ++++++++++++---------------------------------
>   3 files changed, 69 insertions(+), 51 deletions(-)
>   create mode 100644 arch/mips/mm/page-funcs.S
>

Re: [PATCH] MIPS: Refactor 'clear_page' and 'copy_page' functions.

[Ralf Baechle]

On Wed, May 30, 2012 at 11:10:23AM -0700, David Daney wrote:

> On 05/24/2012 01:38 PM, Steven J. Hill wrote:
> >From: "Steven J. Hill"<sjhill@mips.com>
> >
> >Remove usage of the '__attribute__((alias("...")))' hack that aliased
> >to integer arrays containing micro-assembled instructions. This hack
> >breaks when building a microMIPS kernel. It also makes the code much
> >easier to understand.
> >
> >Signed-off-by: Steven J. Hill<sjhill@mips.com>
> 
> Looks good to (and even works for) me:
> 
> Acked-by: David Daney <david.daney@cavium.com>

I have to admit that the attribute hack was a desperate attempt at
avoiding the last bit of assembler code for the page functions.  But somehow
the patch isn't quite ripe yet.  Building malta_defconfig from
7a3434a78b36be2d398a46fb505a3196a9df4a60 with this patch applied on top
I'm getting:

  MODPOST 413 modules
ERROR: "copy_page" [fs/fuse/fuse.ko] undefined!
ERROR: "clear_page" [fs/fuse/fuse.ko] undefined!
ERROR: "clear_page" [drivers/net/ethernet/toshiba/tc35815.ko] undefined!

  Ralf

Re: [PATCH] MIPS: Refactor 'clear_page' and 'copy_page' functions.

[Ralf Baechle]

On Wed, May 30, 2012 at 10:01:41PM +0100, Ralf Baechle wrote:

> > On 05/24/2012 01:38 PM, Steven J. Hill wrote:
> > >From: "Steven J. Hill"<sjhill@mips.com>
> > >
> > >Remove usage of the '__attribute__((alias("...")))' hack that aliased
> > >to integer arrays containing micro-assembled instructions. This hack
> > >breaks when building a microMIPS kernel. It also makes the code much
> > >easier to understand.
> > >
> > >Signed-off-by: Steven J. Hill<sjhill@mips.com>
> > 
> > Looks good to (and even works for) me:
> > 
> > Acked-by: David Daney <david.daney@cavium.com>
> 
> I have to admit that the attribute hack was a desperate attempt at
> avoiding the last bit of assembler code for the page functions.  But somehow
> the patch isn't quite ripe yet.  Building malta_defconfig from
> 7a3434a78b36be2d398a46fb505a3196a9df4a60 with this patch applied on top
> I'm getting:
> 
>   MODPOST 413 modules
> ERROR: "copy_page" [fs/fuse/fuse.ko] undefined!
> ERROR: "clear_page" [fs/fuse/fuse.ko] undefined!
> ERROR: "clear_page" [drivers/net/ethernet/toshiba/tc35815.ko] undefined!

And with that fixed (trivial) I'm getting:

  AS      arch/mips/mm/page-funcs.o
arch/mips/mm/page-funcs.S: Assembler messages:
arch/mips/mm/page-funcs.S:29: Warning: .end symbol does not match .ent symbol.
arch/mips/mm/page-funcs.S:48: Warning: .end symbol does not match .ent symbol.
{standard input}: Error: .size expression for clear_page does not evaluate to a constant
{standard input}: Error: .size expression for copy_page does not evaluate to a constant

  Ralf